It is common practice to use liquid electrolytes in electrochemical devices such as a primary battery, a secondary battery and a capacitor. However, the liquid electrolytes have a drawback in that they are likely to cause a liquid leakage to thereby render their long-term reliability unsatisfactory.
The use of a solid electrolyte is known as means for solving this problem. When the solid electrolyte is used in the above electrochemical device, not only can the liquid leakage be avoided to thereby provide a highly reliable device but also the device itself can be miniaturized with its weight reduced. In recent years, various polymeric solid electrolytes (solid polymer electrolytes) have been investigated as providing the above solid electrolyte. The polymeric solid electrolyte not only possesses such a flexibility that its versatile use can be effected irrespective of a volume change which occurs in the course of ion electron exchange reaction between an electrode and the polymeric solid electrolyte but also has the above characteristics of the solid electrolyte. A composite of a polyethylene oxide having a polyether structure and an alkali metal salt such as a lithium salt is known as providing an example of the above polymeric solid electrolyte. Further, Japanese Patent Laid-open Publication No. 5(1993)-25353 describes a polymeric solid electrolyte consisting mainly of a polyoxyalkylene diester compound, a polymethoxyoxyalkylene ester compound, a crosslinked resin of a copolymer with an oxy compound having a double bond and an inorganic salt. Still further, Japanese Patent Laid-open Publication No. 6(1994)-223842 describes a polymeric solid electrolyte composed of an organic polymer having carbonate groups as a functional group and a metal salt.
However, the ionic conductivity of the solid electrolyte is generally lower than that of the liquid electrolyte, so that it has been difficult to obtain primary and secondary batteries exhibiting excellent discharge characteristics from the solid electrolyte. In the above circumstances, there is a demand for the development of a polymeric solid electrolyte which can satisfy requirements for, for example, enhanced ionic conductivity and electrochemical stability.